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Posts Tagged ‘evolution’

The cat’s back!

Posted in Frozen Mammals, Guestsicle, tagged , , , , , , on November 23, 2016| Leave a Comment »

(Marcela with some furry friends; photo by Oliver Siddon)

(Marcela with some felid friends; photo by Oliver Siddon)

A guest post by Marcela Randau (m.randau@ucl.ac.uk)

Stomach-Churning Rating: 1/10; just bones and data plots!

It is often said that all cats are very similar in terms of their skeletal morphology (“a cat is a cat is a cat”). But is this really the case? It may be if only gross, qualitative anatomy is taken into consideration, i.e., if you just eyeball the skeletons of tigers and lions you might find yourself not knowing which one is which. But with huge advances in technology that allows for extracting detailed shape information off a structure (e.g., a skull) and for analysing this information (‘Geometric Morphometrics’), it has become more and more possible to distinguish between relatively similar forms – which may be from distinct species, separate sexes, or even just different populations of the same taxon.

And it is reasonable to think that cat skeletons might be a lot more different than what meets the eye, as for a lineage of apparently similarly built animals, with not that much variation in diet  (all cats are hypercarnivores) there is substantial variation in body mass (over 300-fold just in living species!) and in ecology across cat species. From the cursorial cheetah to the arboreal clouded leopard, felids present a wide range of locomotory adaptations. Yes, all cats can climb, but some do it better than others: think lion versus margay (yes, they do descend trees head-first). As hypercarnivores, all cats are meat specialists, but they also change with regards to how big their prey is, with a general and sometimes-not-so-black-and-white three-tier classification into small, mixed and large prey specialists. The rule of thumb is ‘if you are lighter than ~20-25 kg, hunt small stuff. If you are heavier than that, hunt BIG BIG things; bigger than yourself. And if you are in the middle ground, hunt some small-ish things, some big-ish things, and things about your size. Well, -ish’ – their prey size preference has a lot to do with energetic constraints (have a look at Carbone et al. 1999; and Carbone et al. 2007, if you’re interested in this). But the fun bit here is that form sometimes correlates quite strongly with function, so we should be able to find differences in some of their bones that carry this ecological signal.

Indeed, for a while now, we have known that the shape of the skull and limbs of felids can tell us a lot about how they move and how big their prey is (Meachen-Samuels and Van Valkenburgh 2009, 2009), but a large proportion of their skeleton has been largely ignored: we don’t know half as much about ecomorphology and evolution of the vertebral column. Well, it was time we changed this a bit! As the PhD student in the Leverhulme-funded ‘Walking the cat back’ (or more informally, “Team Cat”) project, I’ve spend a big chunk of my first two years travelling around the world (well, ok, mainly to several locations in the USA) carrying a heavy pellet case containing my working tool, a Microscribe, to collect 3-D landmarks (Fig. 1) across the presacral vertebral column of several cat species. And some of first results are just out! Check them out by reading our latest paper, “Regional differentiation of felid vertebral column evolution: a study of 3D shape trajectories” in the Organisms Diversity and Evolution journal (Randau, Cuff, et al. 2016).

cheetah-verts

Fig. 1: Different vertebral morphologies and their respective three-dimensional landmarks. Vertebral images are from CT scans of Acinonyx jubatus (Cheetah, USNM 520539)

Building from results based on our linear vertebral data from the beginning of the year (Randau, Goswami, et al. 2016), the 3-D vertebral coordinates carry a lot more information and we were able to describe how this complex shape-function relationship takes place throughout the axial skeleton (in cats at least) in much better detail than our prior study did. One of the difficulties in studying serial structures such as the vertebral column is that some clades present variation in vertebral count which makes it less straightforward to compare individual vertebrae or regions across species. However, mammals are relatively strongly constrained in vertebral count, and Felidae (cats; living and known fossils) show no variation at all, having 27 presacral vertebrae. So adaptation of the axial skeleton in mammals has been suggested to happen by modification of shape rather than changes in vertebral number.

Using a variety of geometric morphometric analyses, under a phylogenetically informative methodology, we have shown that there is clear shape and functional regionalisation across the vertebral column, with vertebrae forming clusters that share similar signal. Most interestingly, the big picture of these results is a neck region which is either very conservative in shape, or is under much stronger constraints preventing it from responding to direct evolutionary pressures, contrasting with the ‘posteriormost’ post-diaphragmatic tenth thoracic (T10) to last lumbar (L7) vertebral region, which show the strongest ecological correlations.

We were able to analyse shape change through functional vertebral regions, rather than individual vertebrae alone, by making a novel application of a technique called the ‘Phenotypic Trajectory Analysis’, and demonstrated that the direction of vertebral shape trajectories in the morphospace changes considerably between both prey size and locomotory ecomorphs in cats, but that the amount of change in each group was the same. It was again in this T10-L7 region that ecological groups differed the most in vertebral shape trajectories (Fig. 2).

pta-cats

Figure 2: Phenotypic trajectory analysis (PTA) of vertebrae in the T10 – L7 region grouped by prey size (A) and locomotory (B) categories.

So in the postcranial morphology of cats can be distinguished, changing its anatomy in order to accommodate the different lifestyles we see across species. But the distinct parts of this structure respond to selection differently. The next step is figuring out how that might happen and we are working on it.

While Team Cat continues to investigate other biomechanical and evolutionary aspects of postcranial morphology in this interesting family, we’ve been able to discuss some of these and other results in a recent outreach event organised by the University College of London Grant Museum of Zoology and The Royal Veterinary College. We called it “Wild Cats Uncovered: movement evolves”. Check how it went here: (https://blogs.ucl.ac.uk/museums/2016/11/17/cheetah-post-mortem/) and here (http://www.rvc.ac.uk/research/research-centres-and-facilities/structure-and-motion/news/wild-cats-uncovered), with even more pics here (https://www.flickr.com/photos/144824896@N07/sets/72157676695634065/).

References used here:

Carbone, C., Mace, G. M., Roberts, S. C., and Macdonald, D. W. 1999. Energetic constaints on the diet of terrestrial carnivores. Nature 402:286-288.

Carbone, C., Teacher, A., and Rowcliffe, J. M. 2007. The costs of carnivory. PLoS biology 5 (2):e22.

Meachen-Samuels, J. and Van Valkenburgh, B. 2009. Craniodental indicators of prey size preference in the Felidae. Biol J Linn Soc 96 (4):784-799.

———. 2009. Forelimb indicators of prey-size preference in the Felidae. Journal of morphology 270 (6):729-744.

Randau, M., Cuff, A. R., Hutchinson, J. R., Pierce, S. E., and Goswami, A. 2016. Regional differentiation of felid vertebral column evolution: a study of 3D shape trajectories. Organisms Diversity and Evolution Online First.

Randau, M., Goswami, A., Hutchinson, J. R., Cuff, A. R., and Pierce, S. E. 2016. Cryptic complexity in felid vertebral evolution: shape differentiation and allometry of the axial skeleton. Zoological Journal of the Linnean Society 178 (1):183-202.

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It’s Raining Jobs!?

Posted in Biomechanics, Exalting Archosauria, Uncategorized, tagged , , , , on July 29, 2016| 4 Comments »

Short post here– I have 4 jobs now opened on my team, 1 short-term one (~4 months or less) and 3 long-term ones (5 years; negotiable down to 2-3 minimum) as follows:

Stomach-Churning Rating: -10/10 Let’s do some SCIENCE!

  1. Research Technician in Vertebrate Anatomical Imaging; until ~1 December 2016 (some flexibility), on our Leverhulme Trust sesamoid bone grant. Lots of flexibility here and on a super fun, established project! Deadline to apply: 11 August (interviews will be 22 August)
  2. Part-time (50%) Research Administrator, on our ERC dinosaur evolution/locomotion grant until 2021. I’m hunting for someone that’s super organized and enthusiastic and not afraid of paperwork (it is EU funding, after all), but there is sure to be some involvement in science communication, too. Deadline to apply: 11 August  (interviews will be 31 August)
  3. Research Technician in Biomechanics; until 2021 as above. This post will not “just” be technical support but hands-on doing science. Some vital experience in biomechanics will be needed as the research will begin very quickly after starting. If the right person applies, we could agree for them to do a part-time PhD or MRes related to the grant research (but that’s not guaranteed in advance). Deadline to apply: 26 August (interviews will be 7/8 September)
  4. Postdoctoral Researcher in Biomechanics; until 2021 as above. This second postdoc on the project will join Dr. Vivian Allen and the rest of my team to push this project forward! I am keenest on finding someone who is good at biomechanical computer simulation, i.e., has already published on work in that general area. But the right person with XROMM (digital biplanar fluoroscopy), other digital imaging and biomechanics experience might fit. Deadline to apply: 23 August (interviews will be 7/8 September)

Update: all jobs have closed for applications.

Update 2: BUT not all the jobs are 5-year contracts. Some may open up again for new people in the future (but not very soon). Stay tuned…

Note that on the bottom of each page linked above, there are Person Specification and Job Description documents that explain more what the jobs are about and what skills we’re looking for in applicants. I strongly encourage any applicants to read these before applying. If those documents don’t describe you reasonably well, it is probably best not to apply, but you can always contact me if you’re not sure.

The project for jobs 2-4 is about testing the “locomotor superiority hypothesis”, an old idea that dinosaurs gained dominance in the Triassic-Jurassic transition because something about their locomotion was better in some way than other archosaurs’. That idea has been dismissed, embraced, ignored and otherwise considered by various studies over the past 40+ years but never really well tested. So in we go, with a lot of biomechanical and anatomical tools and ideas to try to (indirectly) test it! As usual for projects that I do, there is a healthy mix of empirical (e.g. experiments) and theoretical (e.g. models/simulations) research to be done.

Please spread the word if you know of someone right for any of these roles. I am casting a broad net. The next year (and beyond) is going to be a very exciting time on my team, with this big ~£1.9M ERC Horizon 2020 grant starting and lots of modelling, simulation, experiments, imaging and more. Non-EU/EEA/UK people are very welcome to apply– “Brexit” is not expected to affect this project. If you’re not familiar with my team, check out my “mission statement” for what we stand for professionally and as a team. Join us!

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Better Know A Muscle: 1. Caudofemoralis longus

Posted in Better Know A Muscle, Exalting Archosauria, tagged , , , , , , , on February 12, 2016| 15 Comments »

Happy Darwin Day from the frozen tundra sunny but muddy, frosty lands of England! I bring you limb muscles as peace offerings on this auspicious day. Lots of limb muscles. And a new theme for future blog posts to follow up on: starting off my “Better Know A Muscle” (nod to Stephen Colbert; alternative link) series. My BKAM series intends to walk through the evolutionary history of the coolest (skeletal/striated) muscles. Chuck Darwin would not enjoy the inevitable blood in this photo-tour, but hopefully he’d like the evolution. Off we go, in search of better knowledge via an evolutionary perspective!

There is, inarguably, no cooler muscle than M. caudofemoralis longus, or CFL for short. It includes the largest limb muscles of any land animal, and it’s a strange muscle that confused anatomists for many years– was it a muscle of the body (an axial or “extrinsic” limb muscle, directly related to the segmented vertebral column) or of the limbs (an “abaxial” muscle, developing with the other limb muscles from specific regions of the paraxial mesoderm/myotome, not branching off from the axial muscles)? Developmental biologists and anatomists answered that conclusively over the past century: the CFL is a limb muscle, not some muscle that lost its way from the vertebral column and ended up stranded on the hindlimb.

The CFL is also a muscle that we know a fair amount about in terms of its fossil record and function, as you may know if you’re a dinosaur fan, and as I will quickly review later. We know enough about it that we can even dare to speculate if organisms on other planets would have it. Well, sort of…

Stomach-Churning Rating: 8/10. Lots of meaty, bloody, gooey goodness, on and on, for numerous species. This is an anatomy post for those with an appetite for raw morphology.

Let’s start from a strong (and non-gooey) vantage point, to which we shall return. The CFL in crocodiles and most other groups is (and long was) a large muscle extending from much of the front half or so of the tail to the back of the femur (thigh bone), as shown here:

Julia Molnar's fabulous illustration of Alligator's limb muscles, from our 2014 paper in Journal of Anatomy.

Julia Molnar’s fabulous illustration of Alligator‘s limb muscles, from our 2014 paper in Journal of Anatomy. Note the CFL in blue at the bottom right.

As the drawing shows, the CFL has a friend: the CFB. The CFB is a shorter, stumpier version of the CFL restricted to the tail’s base, near the hip. The “B” in its name means “brevis”, or runty. It gets much less respect than its friend the CFL. Pity the poor CFB.

But look closer at the CFL in the drawing above and you’ll see a thin blue tendon extending past the knee to the outer side of the lower leg. This is the famed(?) “tendon of Sutton“, or secondary tendon of the CFL. So the CFL has two insertions, one on the femur and one (indirectly) onto the shank. More about that later.

Together, we can talk about these two muscles (CFL and CFB) as the caudofemoralis (CF) group, and the name is nice because it describes how they run from the tail (“caudo”) to the femur (“femoralis”). Mammal anatomists were late to this party and gave mammal muscles stupidly unhelpful names like “gluteus” or “vastus” or “babalooey”. Thanks.

But enough abstract drawings, even if they rock, and enough nomenclature. Here is the whopping big CFL muscle of a real crocodile:

Huge Nile crocodile, but a relatively small CFL.

Huge Nile crocodile, but a relatively small CFL.

Bigger crocs have smaller legs and muscles.

Bigger crocs have smaller legs and thus smaller leg muscles, relatively speaking. CFL at the top, curving to the left.

The giant Nile croc's CFL muscle removed for measurements.

The giant Nile croc’s CFL muscle removed for measurements. 2.35 kg of muscle! Not shabby for a 278 kg animal.

However, maybe crocodile and other archosaur CFL muscles are not “average” for leggy vertebrates? We can’t tell unless we take an evolutionary tack to the question.

Where did the CFL come from, you may ask? Ahh, that is shrouded in the fin-limb transition‘s mysteries. Living amphibians such as salamanders have at least one CF muscle, so a clear predecessor to the CFL (and maybe CFB) was present before reptiles scampered onto the scene.

But going further back through the CF muscles’ history, into lobe-finned fish, becomes very hard because those fish (today) have so few fin muscles that, in our distant fishy ancestors, would have given rise eventually to the CF and other muscle groups. With many land animals having 30+ hindlimb muscles, and fish having 2-8 or so, there obviously was an increase in the number of muscles as limbs evolved from fins. And because a limb has to do lots of difficult three-dimensional things on land while coping with gravity, more muscles to enable that complex control surely were needed.

OK, so there were CF muscles early in tetrapod history, presumably, anchored on that big, round fleshy tail that they evolved from their thin, finned fishy one — but what happened next? Lizards give us some clues, and their CFL muscles aren’t all that different from crocodiles, so the CFL’s massive size and secondary “tendon of Sutton” seems to be a reptile thing, at least.

Courtesy of Emma Schachner, a large varanid lizard's very freshly preserved CFL and other hindlimb muscles.

Courtesy of Emma Schachner, a large varanid lizard’s very freshly preserved CFL and other hindlimb muscles.

Courtesy of Emma Schachner, zoomed in on the tendons and insertions of the CFL muscle and others.

Courtesy of Emma Schachner, zoomed in on the tendons and insertions of the CFL muscle and others. Beautiful anatomy there!

Looking up at the belly of a basilisk lizard and its dissected right leg, with the end of the CFL labelled.

Looking up at the belly of a basilisk lizard and its dissected right leg, with the end of the CFL labelled. It’s not ideally dissected here, but it is present.

An unspecified iguanid(?) lizard, probably a juvenile Iguana iguana, dissected and showing its CFL muscle at its end. The muscle would extemd about halfway down the tail, though.

An unspecified iguanid(?) lizard, probably a juvenile Iguana iguana, dissected to reveal its CFL muscle near its attachment to the femur. The muscle would extend further, about halfway down the tail, though.

Let’s return to crocodiles, for one because they are so flippin’ cool, and for another because they give a segue into archosaurs, especially dinosaurs, and thence birds:

A moderate-sized (45kg) Nile crocodile with its CFL muscle proudly displayed.

A moderate-sized (45kg) Nile crocodile with its CFL muscle proudly displayed. Note the healthy sheath of fat (cut here) around the CFL.

American alligator's CFL dominates the photo. Photo by Vivian Allen.

American alligator’s CFL dominates the photo [by Vivian Allen].

Black caiman, Melanosuchus, showing off its CFL muscle (pink "steak" in the middle of the tail near the leg).

Black caiman, Melanosuchus, showing off its CFL muscle (pink “steak” in the middle of the tail near the leg), underneath all that dark armour and fatty superficial musculature.

A closer look at the black caiman's thigh and CFL muscle.

A closer look at the black caiman’s thigh and CFL muscle.

Like I hinted above, crocodiles (and the anatomy of the CFL they share with lizards and some other tetrapods) open a window into the evolution of unusual tail-to-thigh muscles and locomotor behaviours in tetrapod vertebrates.

Thanks in large part to Steve Gatesy’s groundbreaking work in the 1990s on the CFL muscle, we understand now how it works in living reptiles like crocodiles. It mainly serves to retract the femur (extend the hip joint), drawing the leg backwards. This also helps support the weight of the animal while the foot is on the ground, and power the animal forwards. So we call the CFL a “stance phase muscle”, referring to how it mainly plays a role during ground contact and resisting gravity, rather than swinging the leg forwards (protracting the limb; i.e. as a “swing phase muscle”).

The “tendon of Sutton” probably helps to begin retracting the shank once the thigh has moved forward enough, facilitating the switch from stance to swing phase, but someone really needs to study that question more someday.

And thanks again to that same body of work by Gatesy (and some others too), we also understand how the CFL’s anatomy relates to the underlying anatomy of the skeleton. There is a large space for the CFL to originate from on the bottom of the tail vertebrae, and a honking big crest (the fourth trochanter) on the femur in most reptiles that serves as the major attachment point, from which the thin “tendon of Sutton” extends down past the knee.

Femur bones (left side) from an adult ostrich (Left) and Nile crocodile (Right).

Femur bones (left side; rear view) from an adult ostrich (left) and Nile crocodile (right). Appropriate scale bar is appropriate. The fourth trochanter for the CFL is visible in the crocodile almost midway down the femur. Little is left of it in the ostrich but there is a bumpy little muscle scar in almost the same region as the fourth trochanter, and this is where the same muscle (often called the CFC; but it is basically just a small CFL) attaches.

That relationship of the CFL’s muscular anatomy and the underlying skeleton’s anatomy helps us a lot! Now we can begin to look at extinct relatives of crocodiles; members of the archosaur group that includes dinosaurs (which today we consider to include birds, too), and things get even more interesting! The “tendon of Sutton”, hinted at by a “pendant” part of the fourth trochanter that points down toward the knee, seems to go away multiple times within dinosaurs. Bye bye! Then plenty more happens:

A large duckbill dinosaur's left leg, with a red line drawn in showing roughly where the CFL would be running, to end up at the fourth trochanter. Many Mesozoic dinosaurs have skeletal anatomy that indicates a similar CFL muscle.

A large duckbill dinosaur’s left leg, with a red line drawn in showing roughly where the CFL would be running, to end up at the fourth trochanter. Many Mesozoic dinosaurs have skeletal anatomy that indicates a similar CFL muscle.

We can even go so far as to reconstruct the 3D anatomy of the CFL in a dinosaur such as T. rex ("Sue" specimen here; from Julia Molnar's awesome illustration in our 2011 paper), with a fair degree of confidence.

We can even go so far as to reconstruct the 3D anatomy of the CFL in a dinosaur such as T. rex (“Sue” specimen here; from Julia Molnar’s awesome illustration as part of our 2011 paper), with a fair degree of confidence. >180kg steak, anyone?

As we approach birds along the dinosaur lineage, the tail gets smaller and so does the fourth trochanter and thus so must the CFL muscle, until we’re left with just a little flap of muscle, at best. In concert, the hindlimbs get more crouched, the forelimbs get larger, flight evolves and voila! An explosion of modern bird species!

Ozburt (72)

Left femur of an ostrich in side view (hip is toward the right side) showing many muscles that attach around the knee (on the left), then the thin strap of CF muscle (barely visible; 2nd from the right) clinging near the midshaft of the femur.

Another adult ostrich's CF muscle complex, removed for study.

Another adult ostrich’s CF muscle complex, removed for study. Not enough ostrich myology for you yet? Plenty more in this old post! Or this one! Or this one… hey maybe I need to write less about ostriches? The CF muscle complex looks beefy but it’s no bigger than any other of the main hindlimb muscles, unlike the CFL in a crocodile or lizard, which puts everything else to shame!

STILL not enough ostrich for you yet? Take a tour of the major hindlimb muscles in this video:

And check out the limited mobility of the hip joint/femur here. No need for much femur motion when you’re not using your hip muscles as much to drive you forwards:

But I must move on… to the remainder of avian diversity! In just a few photos… Although the CF muscles are lost in numerous bird species, they tend to hang around and just remain a long, thin, unprepossessing muscle:

Chicken's right leg in side view. CFC (equivalent of CFL) muscle outlined and labelled.

Chicken’s right leg in side view. CFC muscle (equivalent of CFL; the ancestral CFB is confusingly called the CFP in birds, as it entirely resides on the pelvis) outlined and labelled.

A jay (species?) dissected to show some of the major leg muscles, including the CF. Photo by Vivian Allen.

A jay (species? I forget) dissected to show some of the major leg muscles, including the CFL-equivalent muscle; again, smallish. [Photo by Vivian Allen]

Finally, what’s up with mammals‘ tail-to-thigh CF-y muscles? Not much. Again, as in birds: smaller tail and/or femur, smaller CF muscles. Mammals instead depend more on their hamstring and gluteal muscles to support and propel themselves forward.

But many mammals do still have something that is either called the M. caudofemoralis or is likely the same thing, albeit almost always fairly modest in size. This evolutionary reduction of the CF muscle along the mammal (synapsid) lineage hasn’t gotten nearly as much attention as that given to the dinosaur/bird lineage’s CFL. Somebody should give it a thoroughly modern phylogenetic what-for! Science the shit outta that caudofemoralis…

Yet, oddly, to give one apparent counter-example, cats (felids) have, probably secondarily, beefed up their CF muscle a bit:

Cats have a pretty large CF muscle in general, and this jaguar is no exception! But mammals still tend to have fairly wimpy tails and thus CF muscles, or they even lose them (e.g. us?).

Cats have a pretty large CF muscle in general, and this jaguar is no exception! But mammals still tend to have fairly wimpy tails and thus CF muscles, or they even lose them (e.g. us?). [photo by Andrew Cuff, I think]

In summary, here’s what happened (click to embeefen):

Better Know A Muscle: The Evolution of M. caudofemoralis (longus)

Better Know A Muscle: the evolution of M. caudofemoralis (longus).

I hope you enjoyed the first BKAM episode!
I am willing to hear requests for future ones… M. pectoralis (major/profundus) is a serious contender.

P.S. It was Freezermas this week! I forgot to mention that. But this post counts as my Freezermas post for 2016; it’s all I can manage. Old Freezermas posts are here.

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GUEST POST: Croc backbones through Deep Time

Posted in Croc-cicles, Exalting Archosauria, Guestsicle, tagged , , , , , , , on November 4, 2015| 6 Comments »

Seeking adaptations for running and swimming in the vertebral columns of ancient crocs

A guest post by Dr. Julia Molnar, Howard University, USA (this comes from Julia’s PhD research at RVC with John & colleagues)

Recently, John and I with colleagues Stephanie Pierce, Bhart-Anjan Bhullar, and Alan Turner described morphological and functional changes in the vertebral column with increasing aquatic adaptation in crocodylomorphs (Royal Society Open Science, doi 10.1098/rsos.150439). Our results shed light upon key aspects of the evolutionary history of these under-appreciated archosaurs.

Stomach-Churning Rating: 5/10; a juicy croc torso in one small photo but that’s all.

Phylogenetic relationships of the three crocodylomorph groups in the study and our functional hypotheses about their vertebrae. * Image credits: Hesperosuchus by Smokeybjb, Suchodus by Dmitry Bogdanov (vectorized by T. Michael Keesey) http://creativecommons.org/licenses/by-sa/3.0

Phylogenetic relationships of the three crocodylomorph groups in the study and our functional hypotheses about their vertebrae. * Image credits: Hesperosuchus by Smokeybjb, Suchodus by Dmitry Bogdanov (vectorized by T. Michael Keesey) http://creativecommons.org/licenses/by-sa/3.0

As fascinating as modern crocodiles might be, in many ways they are overshadowed by their extinct, Mesozoic cousins and ancestors. The Triassic, Jurassic, and early Cretaceous periods saw the small, fast, hyper-carnivorous “sphenosuchians,” the giant, flippered marine thalattosuchians, and various oddballs like the duck-billed Anatosuchus and the aptly named Armadillosuchus. As palaeontologists/biomechanists, we looked at this wide variety of ecological specializations in those species, the Crocodylomorpha, and wanted to know, how did they do it?

Of course, we weren’t the first scientists to wonder about the locomotion of crocodylomorphs, but we did have some new tools in our toolbox; specifically, a couple of micro-CT scanners and some sophisticated imaging software. We took CT and micro-CT scans of five fossil crocodylomorphs: two presumably terrestrial early crocodylomorphs (Terrestrisuchus and Protosuchus), three aquatic thalattosuchians (Pelagosaurus, Steneosaurus, and Metriorhynchus) and a semi-aquatic modern crocodile (Crocodylus niloticus). Since we’re still stuck on vertebrae (see, e.g., here; and also here), we digitally separated out the vertebrae to make 3D models of individual joints and took measurements from each vertebra. Finally, we manipulated the virtual joint models to find out how far they could move before the bones bumped into each other or the joints came apart (osteological range of motion, or RoM).

 

Our methods: get fossil, scan fossil, make virtual fossil and play with it.

Our methods: get fossil (NHMUK), scan fossil, make virtual fossil and play with it.

Above: Video of a single virtual inter-vertebral joint from the trunk of Pelagosaurus typus (NHMUK) showing maximum osteological range of motion in the lateral direction (video). Note the very un-modern-croc-like flat surfaces of the vertebral bodies! (modern crocs have a ball-and-socket spinal joint with the socket on the front end)

While this was a lot of fun, what we really wanted to find out was whether, as crocodylomorphs became specialized for different types of locomotion, the shapes of their vertebrae changed similarly to those of mammalian lineages. For example, many terrestrial mammals have a lumbar region that is very flexible dorsoventrally to allow up-and-down movements during bounding and galloping. Did fast-running crocodylomorphs have similar dorsoventral flexibility? And did fast-swimming aquatic crocodylomorphs evolve a stiffer vertebral column like that of whales and dolphins?

Above: Video of how we modelled and took measurements from the early crocodylomorph Terrestrisuchus gracilis (NHMUK).

Our first results were puzzling. The Nile croc had greater RoM in side-to-side motions, which makes sense because crocodiles mostly use more sprawling postures and are semi-aquatic, using quite a bit of side-to-side motions in life. The part that didn’t make sense was that we found pretty much the same thing in all of the fossil crocodylomorphs, including the presumably very terrestrial Terrestrisuchus and Protosuchus. With their long limbs and hinge-like joints, these two are unlikely to have been sprawlers or swimmers!

So we started looking for other parts of the croc that might affect RoM. The obvious candidate was osteoderms, the bony scales that cover the back. We went back to John’s Freezer and got out a nice frozen crocodile to measure the stiffness of its trunk and found that, sure enough, it was a lot stiffer and less mobile without the osteoderms. If the fairly flexible arrangement of osteoderms in crocodiles had this effect on stiffness, it seemed likely that (as previous authors have suggested; Eberhard Frey and Steve Salisbury being foremost amongst them) the rigid, interlocking osteoderms running from head to tail in early crocodylomorphs would really have put the brakes on their ability to move their trunk in certain ways.

Testing stiffness of crocodile trunks to learn the effects of osteoderms, skin, muscles, and ribs. We hung metric weights from the middle of the trunk and measured how much it flexed (Ɵ), then removed bits and repeated.

Testing the stiffness of (Nile) crocodile trunks to learn the effects of osteoderms, skin, muscles, and ribs. We hung metric weights from the middle of the trunk and measured how much it flexed (Ɵ), then removed bits and repeated. Click to em-croccen.

Another cool thing we found was new evidence of convergent evolution to aquatic lifestyles in the spines of thalattosuchians. The more basal thalattosuchians, thought to have been near-shore predators, had stiffness and RoM patterns similar to Crocodylus. But Metriorhynchus, which probably was very good at chasing down fast fish in the open ocean, seems to have had greater stiffness. (The stiffness estimates come from morphometrics and are based on modern crocodiles; see here again, or just read the paper already!) A stiff vertebral column can be useful for a swimmer because it increases the body’s natural frequency of oscillation, and faster oscillation means faster swimming (think tuna, not eel). The same thing seems to have happened in other secondarily aquatic vertebrate lineages such as whales, ichthyosaurs, and mosasaurs.

So, our results were a mixed bag of adaptations particular to crocs and ones that seem like general vertebrate swimming specializations. Crocodylomorphs are important because they are the only group of large vertebrates other than mammals that has secondarily aquatic members and has living members with a reasonably similar body plan, allowing us to test hypotheses in ways that would arguably be impossible for, say, non-avian dinosaurs and birds. The take-home message: crocodylomorphs A) are awesome, and B) can teach us a lot about how vertebrates adapt to different modes of life.

Another take on this story is on our lab website here.

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What’s In John’s Genome?

Posted in Geeking Out, tagged , , , on June 2, 2015| 2 Comments »

Like many people, I’ve sprung for a personal genomics service lately, in my case “23 and me“. There are deeper reasons for doing it, such as finding out anything more about the genetic basis of my health problems and getting my child advance warning if there’s evidence of heritable risks, but curiosity was a big part of the decision. And hey, as a palaeontology fan I want to know how much Neanderthal is in me, because that’s just cool how sexy our two species were together. Well, here’s what I found out! Part of my obligatory “What’s In John’s [X]” series…

Stomach-Churning Rating: 0/10 unless you hate genes, but that’s pretty futile if you do.

First off, let’s explore my evolutionary history within Homo sapiens:

ancestry

 

For the benefit of those that don’t want to screen-squint or click to emzoomen, I’m 99.9% European ancestry in terms of modern populations’ genomic similarity. I’m mostly Northern European, with around 3% Southern and <1% Eastern. The <0.1% West African and Native American ancestries (on my chromosomes 6 and 10, I discerned) are just a smidgen, but I’m still happy to hear of them. I like being a mutt, even if mostly (~69%) a British-Irish and French-German mutt. I expected to find a bit more Scandinavian vestiges in my genome than the 0.7%, based on what little I know of my genealogy, but the 25.5% “broadly Northern European” could cover that.

Like maternal haplogroups? Welcome to my clan, D2 (no relation to D-12…):

haplogroupD2

D2’s like to stalk Mammuthus columbi and run from Smilodon fatalis or terror-birds.

Paternal haplogroups (from my freezer-burned, shrivelled little Y chromosome) are fun, too! Especially R1a1a; it’s the hip haplogroup to hang with:

haplogroupR1a1aWe R1a1a’s enjoy the rich flavour of a Megaloceros giganteus.

All that slaughtering of megafauna and perusing phylogenies was tiring. How about we sing the song of my genome?

Well, modern people are boring, even the migratory ass-kicking Ice Age ones. What going on inside me, and outside of Homo sapien? Check it out:

Neanderthal_and_proud

Chest-thumping caveman dance ensues! This was the result that got me the most excited. I’m worthy of wearing this shirt! 95th percentile, W00T!

3.1%NeanderthalYEAH

(then I found out my wife has more Neanderthal, and I was deflated… no fair! LOLZ.)

So anyway, I’m not just a bland European (not that any human’s ancestry is likely “bland” anyhow). Sweet! The ancestry results alone were interesting enough to make me feel like I got my £125 worth.

How about genetic markers for funky traits?

traits

OK, no booze-flushing reaction or lactose issues, I knew that; bitter or asparagus tastes and smells, sure I knew that; blonde and blue-eyed: check; earwax: eew but kinda neat; sprinty muscles, that makes a lot of sense (I love to sprint; not so much endurance running)… baldness: thanks. Thanks a lot, ancestors! Nice try, curly-haired ur-Hutchinsons, but your coiffured efforts were for naught in my case.

Norovirus: OK I’ll try to avoid youse guys. Duly noted. I’m not a fan of vomiting, despite what my college friends might tell you if asked.

Caffeine “fast metabolizer”– hell yes! No doubt about that. I can take about 1 shot of Espresso in the morning and then I’m done; I’ve become extremely sensitive to caffeine. But the good news for that gene marker is that my alleles “didn’t increase subjects’ heart attack risk” with moderate caffeine intake, and indeed some coffee might even be prophylactic. I don’t intend to test that, though. My days of quaffing a pot of coffee before fraternity parties are long gone.

Overall, the traits stuff was intriguing but held no real surprises. “Subjects averaged 0.3 – 0.7 centimeters shorter than typical height” for one genetic marker is a good example, considering my altitudinally-enhanced morphology, of how genes aren’t necessarily simple determinants of fate.

With trepidation, I turn to genomic markers of my health tendencies:

genetics

Not much going on there. But wait… Looking closer…

Alz

D’oh. But not a big surprise; my mother died of Alzheimer’s so it was at least 50/50 for me. And still not a fate set in stone amino acids, but I’m more motivated now to live it up in my youth! There’s genetic destiny, genetic tendency, and then personal choice. I’ll do what I can with the latter.

Gene products can determine how we react to different chemicals, and I take my share, so I was keen to see what 23andme dug up. It was fascinating:

health

Without boring you with my prescription list, I’m sensitive to several hugely important drugs I take or have taken before. My GP doctor was keen to know this! I feel like this was worth the cost of the genome service to know all these caveats about my metabolism of pharmaceuticals.

So, that’s what I’ve found by rummaging around my genome. I’ve also used the ancestry tools in 23andme to find names of some 4th/5th cousins (who also did the 23andme genome service) around the eastern USA, which is where a lot of my ancestors settled in the 18th-19th centuries, I recall being told.

I don’t feel very worried about abuse of my genomic data by corporations, or other privacy issues related to this. Maybe I should. I feel like having my genome data in my possession, and likely insights 23andme or other services will give me using it in the future, are worth the risks.

If you’ve used a personal genome service of any kind and want to share your tales, go for it in the Comments!

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Deck the ‘Nets With PeerJ Papers

Posted in Exalting Archosauria, tagged , , , , , , , , , on December 23, 2014| 7 Comments »

Deck the ‘Nets With PeerJ Papers— please sing along!

♬Deck the ‘nets with PeerJ papers,
Fa la la la la, la la la la.
‘Tis the day to show our labours,
Fa la la la la, la la la la.

Downloads free; CC-BY license,
Fa la la, la la la, la la la.
Read the extant ratite science,
Fa la la la la, la la la la.

See the emu legs before you
Fa la la la la, la la la la.
Muscles allometric’ly grew.
Fa la la la la, la la la la.

Follow the evolvin’ kneecaps
Fa la la la la, la la la la.
While we dish out ratite recaps 
Fa la la la la, la la la la.

Soon ostrich patellar printing
Fa la la la la, la la la la.
Hail anat’my, don’t be squinting
Fa la la la la, la la la la.

Dissections done all together
Fa la la la la, la la la la.
Heedless of the flying feathers,
Fa la la la la, la la la la♪

(alternate rockin’ instrumental version)

Stomach-Churning Rating: 5/10: cheesy songs vs. fatty chunks of tissue; there are no better Crimbo treats!

Today is a special day for palaeognath publications, principally pertaining to the plethora of published PeerJ papers (well, three of them anyway) released today, featuring my team’s research! An early Crimbo comes this year in the form of three related studies of hind limb anatomy, development, evolution and biomechanics in those flightless feathered freaks of evolutionary whimsy, the ratites! And since the papers are all published online in PeerJ (gold open access), they are free for anyone with internet access to download and use with due credit. These papers include some stunning images of morphology and histology, evolutionary diagrams, and a special treat to be revealed below. Here I’ll summarize the papers we have written together (with thanks to Leverhulme Trust funding!):

1) Lamas, L., Main, R.P., Hutchinson, J.R. 2014. Ontogenetic scaling patterns and functional anatomy of the pelvic limb musculature in emus (Dromaius novaehollandiae). PeerJ 2:e716 http://dx.doi.org/10.7717/peerj.716 

My final year PhD student and “emu whisperer” Luis Lamas has published his first paper with co-supervisor Russ Main and I. Our paper beautifully illustrates the gross anatomy of the leg muscles of emus, and then uses exhaustive measurements (about 6524 of them, all done manually!) of muscle architecture (masses, lengths, etc.) to show how each of the 34 muscles and their tendons grew across a more than tenfold range of body mass (from 6 weeks to 18 months of age). We learned that these muscles get relatively, not just absolutely, larger as emus grow, and their force-generating ability increases almost as strongly, whereas their tendons tend to grow less quickly. As a result, baby emus have only about 22% of their body mass as leg muscles, vs. about 30% in adults. However, baby emus still are extremely athletic, more so than adults and perhaps even “overbuilt” in some ways.

This pattern of rapidly growing, enlarged leg muscles seems to be a general, ancestral pattern for living bird species, reflecting the precocial (more independent, less nest-bound), cursorial (long-legged, running-adapted) natural history and anatomy, considering other studies of ostriches, rheas, chickens and other species close to the root of the avian family tree. But because emus, like other ratites, invest more of their body mass into leg muscles, they can carry out this precocial growth strategy to a greater extreme than flying birds, trading flight prowess away for enhanced running ability. This paper adds another important dataset to the oft-neglected area of “ontogenetic scaling” of the musculoskeletal system, or how the locomotor apparatus adapts to size-/age-related functional/developmental demands as it grows. Luis did a huge amount of work for this paper, leading arduous dissections and analysis of a complex dataset.

Superficial layer of leg muscles in an emu, in right side view.

Superficial layer of leg muscles in an emu, in right side view. Click any image here to emu-biggen. The ILPO and IC are like human rectus femoris (“quads”); ILFB like our biceps femoris (“hams”); FL, GM and GL much like our fibularis longus and gastrocnemius (calf) muscles, but much much bigger! Or, perhaps FL stands for fa la la la la?

Data for an extra set of emus studied by coauthor Russ Main in the USA, which grew their muscles similarly to our UK group. The exponents (y-axis) show how much more strongly the muscles grown than isometry (maintaining the same relative size), which is the dotted line at 1.0.

Data for an extra set of emus studied by coauthor Russ Main in the USA, which grew their muscles similarly to our UK group. The exponents (y-axis) show how much more strongly the muscles grew than isometry (maintaining the same relative size), which is the dotted line at 1. The numbers above each data point are the # of individuals measured. Muscle names are partly above; the rest are in the paper. If you want to know them, we might have been separated at birth!

2) Regnault, S., Pitsillides, A.A., Hutchinson, J.R. 2014. Structure, ontogeny and evolution of the patellar tendon in emus (Dromaius novaehollandiae) and other palaeognath birds. PeerJ 2:e711 http://dx.doi.org/10.7717/peerj.711

My second year PhD student Sophie Regnault (guest-blogger here before with her rhino feet post) has released her first PhD paper, on the evolution of kneecaps (patellae) in birds, with a focus on the strangeness of the region that should contain the patella in emus. This is a great new collaboration combining her expertise in all aspects of the research with coauthor Prof. Andy Pitsillides‘s on tissue histology and mine on evolution and morphology. This work stems from my own research fellowship on the evolution of the patella in birds, but Sophie has taken it in a bold new direction. First, we realized that emus don’t have a patella– they just keep that region of the knee extensor (~human quadriceps muscle) tendon as a fatty, fibrous tissue throughout growth, showing no signs of forming a bony patella like other birds do. This still blows my mind! Why they do this, we can only speculate meekly about so far. Then, we surveyed other ratites and related birds to see just how unusual the condition in emus was. We discovered, by mapping the form of the patella across an avian family tree, that this fatty tendon seems to be a thing that some ratites (emus, cassowaries and probably the extinct giant moas) do, whereas ostriches go the opposite direction and develop a giant double-boned kneecap in each knee (see below), whereas some other relatives like tinamous and kiwis develop a more “normal”, simple flake-like bit of bone, which is likely the state that the most recent common ancestor of all living birds had.

There’s a lot in this paper for anatomists, biomechanists, palaeontologists, ornithologists, evo-devo folks and more… plenty of food for thought. The paper hearkens back to my 2002 study of the evolution of leg tendons in tetrapods on the lineage that led to birds. In that study I sort of punted on the question of how a patella evolved in birds, because I didn’t quite understand that wonderful little sesamoid bone. And now, 12 years later, we do understand it, at least within the deepest branches of living birds. What happened further up the tree, in later branches, remains a big open subject. It’s clear there were some remarkable changes, such as enormous patellae in diving birds (which the Cretaceous Hesperornis did to an extreme) or losses in other birds (e.g., by some accounts, puffins… I am skeptical)– but curiously, patellae that are not lost in some other birds that you might expect (e.g., the very non-leggy hummingbirds).

Fatty knee extensor tendon of emus, lacking a patella. The fatty tissue is split into superficial (Sup) and deep regions, with a pad corresponding to the fat pad in other birds continuous with it and the knee joint meniscus (cushioning pad). The triceps femoris (knee extensor) muscle group inserts right into the fatty tendon, continuing over it. A is a schematic; B is a dissection.

Fatty knee extensor tendon of an emu, showing the absence of a patella. The fatty tissue is split into superficial (Sup) and deep regions, with a pad corresponding to the fat pad in other birds continuous with it and the knee joint meniscus (cushioning pad). The triceps femoris (knee extensor) muscle group inserts right into the fatty tendon, continuing on over it. A is a schematic; B is a dissection.

Sectioning of a Southern Cassowary's knee extensor tendon, showing: A Similar section as in the emu image above. revealing similar regions and fibrous tissue (arrow), with no patella, just fat; and B, with collagen fibre bundles (col), fat cells (a), and cartilage-like tissue (open arrows) labelled.

Sectioning of a Southern Cassowary’s knee extensor tendon, showing: A, Similar section as in the emu image above. revealing similar regions and fibrous tissue (arrow), with no patella, just fat; and B, With collagen fibre bundles (col), fat cells (a), and cartilage-like tissue (open arrows) labelled.

Evolution of patellar form in birds. White branches indicate no patella, blue is a small flake of bone for a patella, green is something bigger, yellow is a double-patella in ostriches, and grey is uncertain. Note the uncertainty and convergent evolution of the patella in ratite birds, which is remarkable but fits well with their likely convergent evolution of flightlessness and running adaptations.

Evolution of patellar form in birds. White branches indicate no patella, blue is a small flake of bone for a patella, green is something bigger, yellow is a double-patella in ostriches, black is a gigantic spar of bone in extinct Hesperornis and relatives, and grey is uncertain. Note the uncertainty and convergent evolution of the patella in ratite birds (Struthio down to Apteryx), which is remarkable but fits well with their likely convergent evolution of flightlessness and running adaptations.

3) Chadwick, K.P., Regnault, S., Allen, V., Hutchinson, J.R. 2014. Three-dimensional anatomy of the ostrich (Struthio camelus) knee joint. PeerJ 2:e706 http://dx.doi.org/10.7717/peerj.706

Finally, Kyle Chadwick came from the USA to do a technician post and also part-time Masters degree with me on our sesamoid grant, and proved himself so apt at research that he published a paper just ~3 months into that work! Vivian Allen (now a postdoc on our sesamoid bone grant) joined us in this work, along with Sophie Regnault. We conceived of this paper as fulfilling a need to explain how the major tissues of the knee joint in ostriches, which surround the double-patella noted above, all relate to each other and especially to the patellae. We CT and MRI scanned several ostrich knees and Kyle made a 3D model of a representative subject’s anatomy, which agrees well with the scattered reports of ostrich knee/patellar morphology in the literature but clarifies the complex relationships of all the key organs for the first time.

This ostrich knee model also takes Kyle on an important first step in his Masters research, which is analyzing how this morphology would interact with the potential loads on the patellae. Sesamoid bones like the patella are famously responsive to mechanical loads, so by studying this interaction in ostrich knees, along with other studies of various species with and without patellae, we hope to use to understand why some species evolved patellae (some birds, mammals and lizards; multiple times) and why some never did (most other species, including amphibians, turtles, crocodiles and dinosaurs). And, excitingly for those of you paying attention, this paper includes links to STL format 3D graphics so you can print your own ostrich knees, and a 3D pdf so you can interactively inspect the anatomy yourself!

(A) X-ray of an ostrich knee in side view, and (B) labelled schematic of the same.

Ostrich knee in side view: A, X-ray, and (B) labelled schematic.

3D model of an ostrich knee, showing: A, view looking down onto the top of the tibia (shank), with the major collateral ligaments (CL), and B, view looking straight at the front of the knee joint, with major organs of interest near the patella, sans muscles.

3D model of an ostrich knee, showing: A, View looking down onto the top of the tibia (shank), with the major collateral ligaments (CL), and B, View looking straight at the front of the knee joint, with major organs of interest near the patella, sans muscles.

You can view all the peer review history of the papers if you want, and that prompts me to comment that, as usual at PeerJ (full disclosure: I’m an associate editor but that brings me £0 conflict of interest), the peer review quality was as rigorous at a typical specialist journal, and faster reviewing+editing+production than any other journal I’ve experienced. Publishing there truly is fun!

Merry Christmas and Happy Holidays — and good Ratite-tidings to all!

And stay tuned- the New Year will bring at least three more papers from us on this subject of ratite locomotion and musculoskeletal anatomy!

♬Should auld palaeognathans be forgot, 
And never brought for scans? 
Should publications be soon sought, 
For auld ratite fans!♪

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Aren’t Adaptations Special?

Posted in RANT, tagged , , , on September 24, 2014| 9 Comments »

Let's play find-the-spandrel!

Let’s play find-the-spandrel!

We just passed the 35th anniversary of the publication of Gould and Lewontin’s classic, highly cited, highly controversial essay (diatribe?), “The spandrels of San Marco and the Panglossian paradigm: a critique of the adaptationist programme.” The 21st of September 1979 was the fateful date. Every PhD student in biology should read it (you can find pdfs here— this post assumes some familiarity with it!) and wrestle with it and either love it or hate it- THERE CAN BE NO MIDDLE GROUND! With some 5405 citations according to Google Scholar, it has generated some discussion, to put it lightly. Evolutionary physiologists and behaviourists who were working at the time it came out have told me stories of how it sent (and continues to send) shockwaves through the community. Shockwaves of “oh crap I should have known better” and “Hell yeah man” and “F@$£ you Steve,” more or less.

I am among those who love “The Spandrels Paper“. I love it despite its many flaws that people have pointed out to seemingly no end- the inaccurate architectural spandrel analogy, the Gouldian discursive (overly parenthetical [I’m a recovering victim of reading too much Gould as an undergrad]) writing style, the perhaps excessive usage of “Look at some classic non-scientific literature I can quote”, the straw men and so on. I won’t belabour those; again your favourite literature search engine can be your guide through that dense bibliography of critiques. I love it because it is so daringly iconoclastic, and because I think it is still an accurate criticism of what a LOT of scientists who do research overlapping with evolutionary biology (that is, much of biology itself) do.

The aspects of The Spandrels Paper that I still think about the most are:

(1) scientists seldom test hypotheses of adaptation; they are quick to label something that is useful to an animal as an adaptation and then move on after rhapsodizing about how cool of an adaptation it is; and

(2) thus alternatives to adaptation, which might be very exciting topics to study in their own right, get less attention or none.

True for #2, evo-devo has flourished by raising the flag of constraint (genetic/developmental/other factors that prevent evolution from going in a certain direction, or even accelerate it in less random directions). That’s good, and there are other examples (genetic drift, we’ve heard about that sometimes), but option #1 still often tends to be the course researchers take. To some degree, labelling something as an adaptation is used as hype, to make it more exciting, I think, in plenty of instances.

Truth be told, much as Gould and Lewontin admitted in their 1979 paper and later ones, natural selection surely forges lineages that have loads of adaptations (even in the strictest sense of the word), and a lot of useful traits of organisms are thus indeed adaptations by any stripe. But the tendency seems to be to assume that this presumptive commonality of adaptations means that we are justified to quickly label traits as adaptations.

Or maybe some researchers just don’t care about rigorous tests of adaptation as they’re keen to do other things. Standards vary. What I wanted to raise in this post is how I tend to think about adaptation:

I think adaptations are totally cool products of evolution that we should be joyous to imagine, document, test and discover. But that means they should be Special. Precious. A cause for celebration, to carefully document by scientific criteria that something is an adaptation in the strictest sense, and not a plesiomorphy/exaptation (i.e. an adaptation at a different level in the evolutionary hierarchy; or an old one put to new uses), spandrel/byproduct, or other alternatives to adaptation-for-current-biological-role.

But that special-ness means testing a hypothesis of adaptation is hard. As many authors waving the flag of The Modern Comparative Method (TMCM) have contended, sciencing truth-to-adaptationist-power by the rules of TMCM takes a lot of work! George Lauder’s 1996 commentary in the great Adaptation book (pdf of the chapter here) outlined a lengthy procedure of  “The Argument from Design“; i.e., testing adaptation hypotheses. At its strictest implementation it could take a career (biomechanics experiments, field studies, fitness measurements, heritability studies, etc.) to test for one adaptation.

Who has time for all that?

The latter question seems maladaptive, placing cart and horse bass-ackwards. If one agrees that adaptations are Special, then one should be patient in testing them. Within the constraints of the practical, to some degree, and different fields would be forced to have different comfort levels of hypothesis testing (e.g. with fossils you can’t ever measure fitness or other components of adaptation directly; that does not mean that we cannot indirectly test for adaptations– with the vast time spans available, one would expect palaeo could do a very good job of it, actually!).

I find that, in my spheres of research, biomechanists in particular tend to be fast to call things they study adaptations, and plenty of palaeontologists do too. I feel like over-usage of the label “adaptation” cheapens the concept, making the discovery of one of the most revered and crucial concepts in all of evolutionary biology seem cheapened and trite. Things that are so easy to discover don’t seem as precious. When everything is awesome, nothing is…

I’ve always hesitated, thanks in part to The Spandrels Paper’s indoctrination, from calling features of animals adaptations, especially in my main research. I nominally do study major ?adaptations? such as terrestrial locomotion at giant body sizes, or the evolution of dinosaurian bipedalism. I searched through my ~80 serious scientific papers lately and found about 50 mentions of “adapt” in an adaptationist, evolutionary context. That’s not much considering how vital the concept is (or I think it is) to my research, but it’s still some mentions that slipped through, most of them cautiously considered– but plenty more times I very deliberately avoided using the term. So I’m no model of best practice, and perhaps I’m too wedded to semantics and pedantry on this issue, but I still find it interesting to think about, and I’ve gradually been headed in the direction of aspect #2 (above in bold) in my research, looking more and more for alternative hypotheses to adaptation that can be tested.

I like talking about The Spandrels Paper and I like some of the criticism of it- that’s healthy. It’s a fun paper to argue about and maybe we should move on, but I still come back to it and wonder how much of the resistance to its core points is truly scientific. I’m entering into teaching time, and I always teach my undergrads a few nuggets of The Spandrels Paper to get them thinking about what lies beyond adaptation in organismal design.

 What do other scientists think? What does adaptation mean (in terms of standards required to test it) to you? I’m curious how much personal/disciplinary standards vary. How much should they?

For the non-scientists, try this on for size: when our beloved Sir David Attenborough (or any science communicator) speaks in a nature documentary about how the otter is “perfectly adapted” to swim after prey underwater, do you buy into that or question it? Should you? (I get documentaries pushing me *all the time* to make statements like this, with a nudge and a wink when I resist) Aren’t scientists funny creatures anyway?

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Dynasty of the Plastic Fishapods

Posted in Two-Dog-Night Tetrapods, tagged , , , , , , on August 28, 2014| 2 Comments »

[This is the original, unedited text of my shorter, tighter (and I think actually better) News & Views piece for Nature, on the paper described below)

Ambitious experimental and morphological studies of a modern fish show how a flexible phenotype may have helped early “fishapods” to make the long transition from finned aquatic animals into tetrapods able to walk on land.

Stomach-Churning Rating: 1/10. Cute fish. Good science. Happy stomachs!

Photo by Antoine Morin, showing Polypterus on land.

Photo by Antoine Morin, showing Polypterus on land.

Napoleon Bonaparte’s military excursions into Egypt in 1798-1799 led a young French naturalist, Ètienne Geoffroy Saint-Hilaire, to cross paths with a strange fish that had paired lungs and could “walk” across land on its stubby, lobelike fins. In 1802, he dubbed this fish “Polyptère bichir”1, today known as the Nile bichir, Polypterus bichir La Cepède 1803. The bichir’s mélange of primitive and advanced traits helped to catapult Geoffroy into scholarly conflict with the reigning naturalist Georges Cuvier back in France and to establish Ètienne as a leading anatomist, embryologist and early evolutionary researcher of repute even today2. Now, on their own excursion under the very “evo-devo” flag that the discoverer of Polypterus helped raise, Canadian scientists Standen et al.3 suggest how the remarkable plasticity of the skeleton of Polypterus (the smaller west African relative of P. bichir, P. senegalus or “Cuvier’s bichir”) reveals a key part of the mechanism that might have facilitated the gradual transition from water to land and thus from “fishapods” to tetrapods (four-limbed vertebrates).

In a bold experiment, the authors raised 149 young bichirs on land and in water for eight months, then studied how they moved on land vs. in water, and also how the ultimate shape of the skeletal elements of the paired front fin bases differed between the land- and water-raised bichirs. Standen et al.3 discovered that both the form and function of the fins’ foundations transformed to better satisfy the constraints of moving on land. Land-acclimated bichirs took faster steps on land, their fins slipped across the substrate less, they held their fins closer to their body, their noses stayed more aloft and their tails undulated less, with less variable motions overall—behaviours that the authors had predicted should appear to enhance walking abilities on land. In turn, the bones of the neck and shoulder region altered their shape to produce a more mobile fin base with greater independence of fin from neck motion, along with improved bracing of the ventral “collarbone” region. These environmentally-induced traits should have fostered the locomotor changes observed in “terrestrialized” fish and aided the animals in resisting gravity, and they represent a common biological phenomenon termed developmental plasticity4,5. Interestingly, the land-reared fish could still swim about as well as the wholly aquatic cohort, so there was not a clear trade-off between being a good swimmer and a good walker, which is surprising.

Considered alone, the developmental plasticity of bichir form and function shows how impressive these amphibious fish are. But Standen et al.’s study3  ventured further, to apply the lessons learned from bichir ontogeny to a phylogenetic context and macroevolutionary question. The phenotypic plasticity during bichir development, they infer, could have been harnessed during the evolutionary transformation of fins for swimming into limbs for walking, in the “fishapod” ancestors of tetrapods. Indeed, bichirs are close to the base of the family tree of fishes6, and other living relatives of tetrapods have reduced or lost their fins (lungfishes) or adapted to strange deep-sea swimming lifestyles, never walking on land (coelacanths). Thus perhaps bichirs and the “fishapod” lineage share what Geoffroy would have called “unity of type”, today termed homology, of their developmental plasticity in response to a land environment. Surveying the fossil record of early “fishapods” and tetrapods, Standen et al.3 found that the macroevolutionary changes of neck and shoulder anatomy in these gradually more land-adapted animals parallel those they observed in terrestrialized Polypterus, providing ancillary support for their hypothesis.

A further test of the application of Polypterus’s plasticity to fossil tetrapods is naturally difficult. However, the “fishapod” lineage has some exceptional examples of fossil preservation. With sufficient sample sizes (e.g. fossil beds that reveal growth series, such as the Late Devonian Miguasha site in Canada7) and palaeoenvironmental gradients in fish or tetrapods, one could imagine performing a rigorous indirect test. Even small samples could be helpful– for example, the early tetrapod Ichthyostega exhibits some developmental changes in its forelimb suggesting that it became more terrestrial as it grew, whereas the related Acanthostega does not evidence such changes8— this hints at some developmental plasticity in the former animal.

During the Devonian period (~360-420 million years ago), were the “fishapod” ancestors of tetrapods floundering about on land now and then, gradually shifting from anatomy and behaviours that were more developmentally plastic (as in bichirs) to ones that were more canalized into the terrestrialized forms and functions that more land-adapted tetrapods retained? An attractive possibility is that the developmental plasticity could have led to fixation (reduction of plasticity), an evolutionary phenomenon called genetic assimilation, which another intellectual descendant of Geoffroy, Conrad Hal Waddington, promoted from the 1950s onwards9, a concept that now enjoys numerous cases of empirical support10 that this one may eventually join.

The nature of the genetic and developmental mechanism that bichirs use to achieve the observed developmental plasticity is still unclear. If it has a high enough degree of heritability, then it could be selected for in cross-generational experiments with bichirs. With sufficient time and luck raising these unusual fish, the hypothesis that their plastic response to a terrestrial environment can become genetically assimilated could be directly tested. This study could thus become an epic exemplar of how genetic assimilation can contribute not only to microevolutionary change but also to major macroevolutionary events, as was presciently suggested in a seminal review of developmental plasticity4.

This genetic assimilation is the Polypterus study’s reasonable speculation, and one that Geoffroy likely would have applauded, all the more for involving his beloved bichirs. Much as Napoleon’s landfall in Egypt was not a lasting success, bichirs never left wholly terrestrial descendants despite their malleable locomotor system. But the same type of plastic developmental mechanism that bichirs use today to make tentative, floppy incursions of the terrestrial realm might have been harnessed by our own “fishapod” forebears, leaving a far more revolutionary dynasty upon the Earth.

 

References

  1.  Geoffroy, E. (1802). Histoire naturelle et description anatomique d’un nouveau genre de poisson du Nil, nommé polyptère. Annales du Muséum d’Histoire Naturelle 1:57-68.
  2. Le Guyader, H., & Grene, M. (2004) Geoffroy Saint-Hilaire: A Visionary Naturalist. Univ. Chicago Press.
  3. Standen, E. M., Du, T. Y., & Larsson, H. C. E. (2014). Developmental plasticity and the origin of tetrapods. Nature, published online.
  4. West-Eberhard, M. J. (1989). Phenotypic plasticity and the origins of diversity. Annual Review of Ecology and Systematics 20:249-278.
  5. Pigliucci, M., Murren, C. J., & Schlichting, C. D. (2006). Phenotypic plasticity and evolution by genetic assimilation. Journal of Experimental Biology 209(12):2362-2367.
  6. Near, T. J., Dornburg, A., Tokita, M., Suzuki, D., Brandley, M. C., & Friedman, M. (2014). Boom and bust: ancient and recent diversification in bichirs (Polypteridae: Actinopterygii), a relictual lineage of ray‐finned fishes. Evolution 68:1014-1026.
  7. Cloutier, R. (2013). Great Canadian Lagerstätten 4. The Devonian Miguasha Biota (Québec): UNESCO World Heritage Site and a Time Capsule in the Early History of Vertebrates.Geoscience Canada40:149-163.
  8. Callier, V., Clack, J. A., & Ahlberg, P. E. (2009). Contrasting developmental trajectories in the earliest known tetrapod forelimbs.Science324:364-367.
  9. Waddington, C. H. (1953). Genetic assimilation of an acquired character. Evolution 7:118-126.
  10. Crispo, E. (2007). The Baldwin effect and genetic assimilation: revisiting two mechanisms of evolutionary change mediated by phenotypic plasticity. Evolution 61:2469-2479.

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A Home for Ontogeny and Phylogeny

Posted in Museums are Cool, tagged , , , , , , , , , , , , , on August 21, 2014| 3 Comments »

Construction of the Phyletisches Museum in Jena, Germany began on Goethe’s birthday on August 28, 1907. The Art Nouveau-styled museum was devised by the great evolutionary biologist, embryologist and artist/howthefuckdoyousummarizehowcoolhewas Ernst Haeckel, who by that time had earned fame in many areas of research (and art), including coining the terms ontogeny (the pattern of development of an organism during its lifetime) and phylogeny (the pattern of evolution of lineages of organisms through time) which feature prominently in the building’s design and exhibits (notice them intertwined in the tree motif below, on the front of the museum). Ontogeny and phylogeny, and the flamboyant artistic sensibility that Haeckel’s work exuded, persist as themes in the museum exhibits themselves. Haeckel also came up with other popular words such as Darwinism and ecology, stem cell, and so on… yeah the dude kept busy.

Cavorting frogs from Haeckel's masterpiece Kunstformen der Natur (1904).

Cavorting frogs from Haeckel’s masterpiece Kunstformen der Natur (1904).

I first visited the Phyletisches Museum about 10 years ago, then again this August. Here are the sights from my latest visit: a whirlwind ~20 minute tour of the museum before we had to drive off to far-flung Wetzlar. All images are click-tastic for embiggenness.

Stomach-Churning Rating: 3/10 for some preserved specimens. And art nouveau.

Willkommen!

Willkommen!

Frog ontogeny, illustrated with gorgeous handmade ?resin? models.

Frog ontogeny, illustrated with gorgeous handmade ?resin? models.

Fish phylogeny, illustrated with lovely artistry.

Phylogeny of Deuterostomia (various wormy things, echinoderms, fish and us), illustrated with lovely artistry.

Phylogeny of fish and tetrapods.

Phylogeny of fish and tetrapods.

Slice of fossil fish diversity.

Slice of fossil fish diversity.

Plenty of chondryichthyan jaws and bodies.

Plenty of chondrichthyan jaws/chondrocrania, teeth and bodies.

Awesome model of a Gulper eel (Saccopharyngiformes).

Awesome model of a Gulper Eel — or, evocatively, “Sackmaul” auf Deutsch (Saccopharyngiformes).

Lobe-finned fishes (Sarcopterygii)- great assortment.

Lobe-finned fishes (Sarcopterygii)- great assortment including a fossil coelacanth.

Lungfish body/model and skeleton.

Lungfish body and skeleton.

Coelacanth!

Coelacanth!

Coelacanth staredown!

Coelacanth staredown!

Fire salamander! We love em, and the museum had several on display- given that we were studying them with x-rays, seeing the skeleton and body together here in this nice display was a pleasant surprise.

On into tetrapods– a Fire Salamander (Salamandra salamandra)! We love ’em, and the museum had several on display- given that we were studying them with x-rays, seeing the skeleton and body together here in this nice display was a pleasant surprise.

A tortoise shell and skeleton, with a goofball inspecting it.

A tortoise shell and skeleton, with a goofball inspecting it.

In a subtle nod to recurrent themes in evolution, the streamlined bodies of an ichthyosaur and cetacean shown in the main stairwell of the museum, illustrating convergent evolution to swimming locomotor adaptations.

In a subtle nod to recurrent themes in evolution, the streamlined bodies of an ichthyosaur and cetacean shown in the main stairwell of the museum, illustrating convergent evolution to swimming adaptations.

Phylogeny of reptiles, including archosaurs (crocs+birds).

Phylogeny of reptiles, including archosaurs (crocs+birds).

Gnarly model of an Archaeopteryx looks over a cast of the Berlin specimen, and a fellow archosaur (crocodile).

Gnarly model of an Archaeopteryx looks over a cast of the Berlin specimen, and a fellow archosaur (crocodile). The only extinct dinosaur on exhibit!

Kiwi considers the differences in modern bird palates: palaeognathous like it and fellow ratites/tinamous (left), and neognathous like most living birds.

Kiwi considers the differences in modern bird palates: palaeognathous like it and fellow ratites/tinamous (left), and neognathous like most living birds.

Echidna skeleton. I can't get enough of these!

Echidna skeleton. I can’t get enough of these!

Skulls of dugong (above) and manatee (below).

Skulls of dugong (above) and manatee (below), Sirenia (seacows) closely related to elephants.

Fetal manatee. Awww.

Fetal manatee. Awww.

Adult Caribbean manatee, showing thoracic dissection.

Adult Caribbean manatee, showing thoracic dissection.

Hyraxes, which Prof. Martin Fischer, longtime curator of the Phyletisches Museum, has studied for many years. Rodent-like elephant relatives.

Hyraxes, which Prof. Martin Fischer, longtime curator of the Phyletisches Museum, has studied for many years. Rodent-like elephant cousins.

Old exhibit at the Phyletisches Museum, now gone: Forelimbs of an elephant posed in the same postures actually measured in African elephants, for the instant of foot touchdown (left pic) and liftoff (right pic). Involving data that we published in 2008!

Old exhibit at the Phyletisches Museum, now gone: Forelimbs of an elephant posed in the same postures actually measured in African elephants, for the instant of foot touchdown (left pic) and liftoff (right pic). Involving data that we published in 2008!

Gorilla see, gorilla do. Notice "bent hip, bent knee" vs. "upright modern human" hindlimb postures in the two non-skeletal hominids.

Eek, primates! Gorilla see, gorilla do. Notice the primitive “bent hip, bent knee” vs. the advanced “upright modern human” hindlimb postures in the two non-skeletal hominids.

Phylogeny of select mammals, including the hippo-whale clade.

Phylogeny of artiodactyl (even-toed) mammals, including the hippo-whale clade.

Hand (manus) of the early stem-whale Ambulocetus.

Hand (manus) of the early stem-whale Ambulocetus.

Carved shoulderblade (scapula) of a bowhead whale (Balaena mysticetus), which apparently Goethe owned. Quite a relic!

Carved shoulderblade (scapula) of a bowhead whale (Balaena mysticetus), which apparently Goethe owned (click to emwhalen and read the fine print). Quite a relic!

One of Haeckel's residences. There is also a well-preserved house of his that one can visit, but I didn't make it there.

One of Haeckel’s residences, across the street from the museum. There is also a well-preserved house of his that one can visit, but I didn’t make it there. I heard it’s pretty cool.

Jena is tucked away in a valley in former East Germany, with no local airport for easy access- but get to Leipzig and take a 1.25 hour train ride and you’re there. Worth a trip! This is where not just ontogeny and phylogeny were “born”, but also morphology as a modern, rigorous discipline. Huge respect is due to Jena, and to Haeckel, whose quotable quotes and influential research still resonate today, in science as well as in art.

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Chilling Out With “Mammoths: Ice Age Giants”

Posted in Frozen Mammals, Museums are Cool, tagged , , , , on June 30, 2014| 11 Comments »

This is the mammoth image I remember, from a 1971 book, with no artist credited. It's actually not as good as I remember, by modern standards at least.

This is the mammoth image I remember, from a 1971 book, with no artist credited. It’s actually not as good as I remember, by modern standards at least.

Mammoths and I go way back, not quite to the Ice Age but at least to the late 1970s with my family’s visits to the University of Wisconsin Geology Museum, and Milwaukee Public Museum, to name two prominent places that inspired me. And one of my favourite science books had a colourful mammoth painting on the cover (above), an image that has stayed with me as awesomely evocative.

Stomach-Churning Rating: 3/10. But there’s a butt below, but that’s too late for you now. And there’s poo and other scatological (attempts at) humour. Otherwise, bones and a baby mammothsicle.

Fast forward to the 2000’s and I’m studying mammoths, along with their other kin amongst the Proboscidea (elephants and relatives). I even bumped into a frozen mammoth in Sapporo, Japan, nine years ago–

Yep. That's what it looks like. Nope, not the front end. That orifice is not the mouth. This is the XXXXX mammoth.

Yep. That’s what it looks like. Nope, not the front end. That dark orifice is not the mouth. This is a mammoth that was found on Bolshoi Lyakhovsky island, in the east Siberian arctic (New Siberian Islands archipelago), in 2003. Just think of finding this and being all excited then realizing, “Jackpot! Wait… Oh man, I just found the ass. I’ve discovered a mammoth bunghole, dammit.” Still, it’s pretty damn amazing, as frozen Ice Age buttocks go. I’d love to find one. I would not be bummed.

found on Bolshoi Lyakhovskiy island in 2003

What I know now that I didn’t realize as a kid, is that a mammoth is an elephant in all but name. Mammoths are more closely related to Asian elephants than either is to African elephants, and all of these elephants are members of the group Elephantidae. If we saw a smallish Columbian mammoth, we’d probably mostly look upon it as similar to a slightly hairy Asian elephant (but a scientist would be able to spot the distinctive traits that each has). Only woolly mammoths adopted the uber-hirsute state that we tend to think of as a “mammoth” trait. Think about it: a big animal would benefit most from a thick hairy insulation in an extremely cold habitat, and Columbian mammoths ranged further south than Woolly ones. No mammoths were radically different from living elephants, unless you count the dwarf ones. But as a kid, like most people do, I saw them as something else: an exotic monster of the past, eerily unlike anything today, and bigger too. And mammoths have the added mystique of the extinct.

Now I see mammoths as neither exotic nor that far in the past. Giant ground sloths, now those are still alien and exotic to me. I don’t get them. I know elephants pretty well, and I can understand mammoths in their light and in light of mammoth fossils. Various mammoth species persisted as late as maybe 10,000 (for the Woolly and Columbian species; the latter seeming to vanish earlier) to <4000 (for isolated Siberian forms) years ago, into quasi-historic times. And only some mammoths got larger than African elephants (Loxodonta) do, such as Columbian mammoths (~10,000 kg or more maximal body mass; Loxodonta is closer to 7-10 tonnes at best).

Lately, coincidence has brought me new knowledge of – and even greater interest in – mammoths.

First, a fortunate last-minute visit to Waco, Texas’s “Mammoth Site” (see my Flickr photo tour here) two weeks ago during a short visit to give a talk in that fine central Texan city.

Second, the subject of today’s post: the Natural History Museum’s new special exhibit “Mammoths: Ice Age Giants“, which is open until 7 September. The exhibit was created by the Field Museum in Chicago, but the NHM has given it a special upgrade under the expert guidance of mammoth guru Prof. Adrian Lister of the NHM, who was very kind to give me a tour of the exhibit.

What follows is primarily a photo-blog post and review of the exhibit, but with some thoughts and facts and anecdotes woven through it. Dark setting, glass cases, caffeination, crowds, and mobile phone camera rather than nice SLR in hand means that the quality isn’t great in my images– but all the more reason to go see the exhibit yourself! All images can be clicked to em-mammoth them.

On entry, one views a mammoth skeleton with a timelapse video backdrop that shows how the landscape (somewhere in USA) has changed since ~10,000 BCE.

On entry, one views a mammoth skeleton with a timelapse video backdrop that shows how the landscape (somewhere in USA) has changed since ~10,000 BCE.

The first part of the exhibit does a nice job of introducing key species of Proboscidea (elephants and their closest extinct relatives), with a phylogeny and timescale to put them into context, starting with the earliest forms:

The first part of the exhibit does a nice job of introducing key species of Proboscidea: from early species like Moeritherium...

from species like the tapir-sized Moeritherium…

Skull of Moeritherium, reconstructed. Not that different from an early sirenian (seacow) in some ways, and general shape.

Skull of Moeritherium, reconstructed. Not that different from an early sirenian (seacow) in some ways, and general shape, whereas still quite a long way from a modern elephant in form– but the hints of tusks and trunk are already there.

...To the early elephantiform Phiomia, here shown as a small animal but I'm told it actually got quite large. And continuing with giant terrestrial taxa...

…To the early elephantiform Phiomia, here shown as a smallish animal but I’m told it actually got quite large. And continuing with giant terrestrial taxa…

I was awed by this reconstruction of the giant early elephantiform relative Deinotherium, with the short, swollen trunk and downturned tusks-- so bizarre!

I was awed by this reconstruction of the huge early elephantiform-relative Deinotherium, with the short, swollen trunk and downturned tusks– so bizarre!

Looking down onto the roof of the mouth of a NHM specimen of Deinotherium.

Looking down onto the roof of the mouth of an NHM specimen of Deinotherium. Big, sharper-edged, almost rhino-like teeth; far from the single mega-molars of modern elephants.

The lower jaw (top) and fairly straight tusk (bottom) of the widespread, early elephantiform Gomphotherium.

The lower jaw (top) and fairly straight tusk (bottom) of the widespread, early elephantiform Gomphotherium.

The big "shovel-tusker" elephantiform Amebelodon. This was one of the earliest stem elephants I learned of as a kid; the odd tusks still give me a sense of wonder.

The big “shovel-tusked” elephantiform Amebelodon. This was one of the earliest stem elephants I learned of as a kid; the odd tusks still stir wonder in me.

Amebelodon lower jaw, sans shovel tusks.

Amebelodon lower jaw, sans shovel tusks. Extended chin looks like some sort of childrens’ fun-slide. To me, anyway.

Next, there are some fun interactive displays of elephant biomechanics!

How would a mammoth hold up its head? This lever demonstration shows how a nuchal ligament helps.

How would a mammoth hold up its head? This lever demonstration shows how a nuchal ligament helps. Tension on the nuchal ligament is a force that acts with a large lever (represented by the big neural spines on the vertebrae around the shoulders, forming the mammoths’ “hump” there), creating a large moment (i.e. torque; rotational force) that holds the head aloft.

I love this robotic elephant trunk demonstration. It captures some of the weirdness of having a muscular hydrostat attached to your lip.

I love this robotic elephant trunk demonstration. It captures some of the weirdness of having a muscular hydrostat attached to your lip and nostrils. Not so easy for a human to control!

But forget the myths about elephants having 40,000 to 150,000 muscles in their trunk. They have three muscle layers: a circumferential one, an oblique one and a longitudinal one. Like any muscles, especially ones this large, the layers each consist of many muscle fibres. That’s where the 40-150k myth comes from, but muscle fibres (cells) are at a more microscopic level than whole muscles (organs). Elephants do have excellent control of their trunks, but it’s not magical. It’s just different.

Then we come to the centrepiece of the exhibit, the ~42,000 year old Woolly mammoth (Mammuthus primigenius) baby “Lyuba“, which the NHM added to the original exhibit in this new version, as a star attraction — and a big win. Adrian Lister related to me how he’d never seen Lyuba in person before (access to it was tightly guarded for years). So when the NHM received the crate and held a press event to open it and reveal Lyuba, a journalist asked Adrian to act excited, to which he responded something like, “I don’t need to act! I’m very excited!” I would be, too! Full story on Lyuba’s arrival, by NHM site here. A key paper on Lyuba by Fisher et al. is here.

Studies of tooth growth in Lyuba reveal her gestation period (like living elephants, around 22 months), season of birth (early spring), and age at death (1 month), among other information.

Studies of tooth growth in Lyuba reveal her gestation period (like living elephants, ~22 months), season of birth (early spring), and age at death (~1 month), among other information.

Here we can see the right ear, which was gnawed off along with the tail by dogs of the reindeer herders that found and retrieved Lyuba. Regardless, there's loads of anatomy preserved! A hump of juvenile "brown fat" atop the head, very strange flanges on the trunk (also visible in 1 other frozen mammoth specimen, but here preserved very clearly!), and more visible postcranially...

Here we can see the right ear, which was gnawed off along with the tail by dogs of the reindeer herders that found and retrieved Lyuba in 2006. Regardless, there’s loads of anatomy preserved!

A hump of juvenile “brown fat” sits atop the head and neck of Lyuba. This probably was  metabolized during growth to warm the baby; brown fat is packed with mitochondria and thereby conducts what is called “non-shivering thermogenesis”. Furthermore, Lyuba has very strange flanges on the trunk (also visible in 1 other frozen mammoth specimen, but here preserved very clearly! What were they used for?). More details are visible postcranially…

The body was naturally “freeze-dried”, with the addition of later rounds of soaking in formalin and ethanol, leaving the body dessicated and stiff, permanently stuck in a lifelike pose as seen below:

Whole view from an exhibit panel (you cannot photograph the specimen but these are fair game!). Here we see hair on the right forearm and remnant of the ear, and the labia and nipples showing it is a female mammoth are also preserved. The head-hump is lost during growth, and the shoulder changes to change the Asian elephant-like convex curvature of the back into the characteristic humped-shoulder form of a mammoth. But ontogeny still reveals the evolutionary connection of Elephas and Mammuthus.

Whole view from an exhibit panel (you cannot photograph the specimen but these are fair game!). Here we see hair on the right forearm and remnant of the ear, and the labia and nipples showing it is a female mammoth are also preserved. The head-hump is lost during growth, and the shoulder changes to change the Asian elephant-like convex curvature of the back into the characteristic humped-shoulder form of a mammoth. But ontogeny still reveals the evolutionary connection of Elephas and Mammuthus.

Lyuba and scientists studying her, which also shows how rigid the carcass is.

Lyuba and scientists studying her, which also shows how rigid the carcass is; one can almost stand it up. Inside the digestive tract, researchers found chewed up plant material that was probably dung eaten by the baby to gain vital bacterial digestive flora, and Lyuba had plenty of body fat and ingested milk, indicating that she did not starve to death. Rather, vivianite in the respiratory tract indicates drowning as the cause of her demise. Perfusion of the body by these vivianites may have helped to preserve the body.

Answering an question the public may be wondering about: is the hype about cloning a mammoth very soon true? Nope. Well addressed, including what to me is the urgent question: would cloning a mammoth be ethical?

Answering a question the public may be wondering about: is the hype about cloning a mammoth very soon true? Nope. Well addressed, including what to me is the urgent question: would cloning a mammoth be ethical?

The fourth part of the exhibit takes on a largely North American focus to first illustrate what mammoths were like biologically, and second to wow the visitor with some huge beasts in full body, full scale glory, as we shall see!

Mammoth hair! These samples and recent molecular studies show that mammoths were not ginger-coloured as we long thought, but rather the ginger color comes as the dark grey-brown-black colour fades postmortem, as a preservational artefact. I didn't know that; cool.

Mammoth hair! These samples and recent molecular studies show that mammoths were not ginger-coloured as we long thought, but rather the ginger color comes as the dark grey-brown-black colour fades postmortem, as a preservational artefact (story here). I didn’t know that; cool.

Mammoth chow!

Mammoth chow! I liked this addition to the exhibit. This brought mammoth ecology closer to home for me.

Mammoth poop!

Mammoth poop!

After the biology explanations, let there be megafauna!

Mammoth skull! A nice one, too.

Mammoth skull! A nice one, too.

Top predators of Ice Age North America: Arctodus (short-faced bear) and Homotherium (sabre-toothed cat).

Top predators of Ice Age North America: Arctodus (short-faced bear– does the short face mean they were happy, unlike a long face? Sorry but they never are shown as very happy, unless it is the joy of whupass) and Homotherium (the other sabre-toothed cat; not the longer-toothed Smilodon).

Skulls of North American megafauna: left to right, top to bottom: horse, short-faced bear, giant sloth, then camel, sabretooth, rabbit, direwolf (viva Ned Stark!), and pronghorn antelope.

Skulls of North American (mega)fauna: left to right, top to bottom: horse, short-faced bear, giant ground sloth, then camel, sabretooth cat, rabbit, direwolf (viva Ned Stark!), and pronghorn antelope.

Mastodon skeleton!

Mastodon (Mammut americanum) skeleton!

Mammoths seem to have been wiped out by a combination of climate change and habitat fragmentation, combined with what this item symbolizes: human hunting. This beautiful piece is the main part of an atlatl, or javelin-hurling lever. It would give Ice Age hunters the extra power they'd need to penetrate mammoth hide and cause mortal injuries.

Mammoths (and perhaps mastodons, etc.) seem to have been wiped out by a combination of climate change and habitat fragmentation, combined with what this item symbolizes: human hunting. This beautiful piece is the main part of an atlatl, or javelin-hurling lever. It would have given Ice Age hunters the extra power they’d need to penetrate mammoth hide and cause mortal injuries. It is also a great tie-in to my recent post on the British Museum’s odd-animals-in-art.

Finally, the exhibit surveys the kinds of mammoths that existed- there is a huge reconstruction of a Columbian mammoth near the mastodon (above), then smaller kinds and discussions of dwarfism, which is another strength of NHM mammoth research:

Woolly mammoth lower jaw (right) and its likely descendant, the pygmy mammoth of the Californian coastline, Mammuthus exilis.

Woolly mammoth lower jaw (right) and its likely descendant, the pygmy mammoth of the Californian coastline, Mammuthus exilis.

The world's smallest mammoth (left), molar tooth compared with that of its much larger ancestor Palaeoloxodon. The status of Mammuthus creticus as a dwarf mammoth from Crete was cemented by Victoria Herridge and colleagues, including Adrian Lister at the NHM.

The world’s smallest mammoth (left), molar tooth compared with that of its much larger ancestor Palaeoloxodon. The status of Mammuthus creticus as a dwarf mammoth from Crete was cemented by Victoria Herridge and colleagues, including Adrian Lister at the NHM.

Pygmy mammoth reconstruction. Shorter than me. I want one!

Pygmy mammoth reconstruction. Shorter than me. I want one!

In the end, from all that proboscidean diversity we were left with just 2 or 3 species (depending on your species concepts; it's probably worth calling the African forest elephant its own species, Loxodonta cyclotis). The exhibit closes with a consideration of their conservation and fate. Ironically, this elephant skull could not be mounted with its tusks on display, because that would be commercializing ivory usage-- even though the whole point of the exhibit's denouement is to explain why elephants need protection!

In the end, from all that glorious proboscidean diversity we were left with just 2 or 3 species of elephantids today (depending on your species concepts; it’s probably worth calling the African forest elephant its own species, Loxodonta cyclotis). The exhibit closes with a consideration of their conservation and fate. Ironically, this elephant skull could not be mounted with its tusks on display, because that would be commercializing ivory usage– even though the whole point of the exhibit’s denouement is to explain why elephants need protection!

Reactions to the exhibit: the photos tell the tale. It’s undeniably great, in terms of showing off the coolness of mammoths, other proboscideans and Ice Age beasties, to the general public. I felt like the factual content and learning potential was good. It didn’t feel at all like pandering to the lowest common denominator like some other exhibits I’ve seen (cough, Dino Jaws, cough). I loved the reconstructions, which were top quality in my opinion. I could have done with some more real skeletons, yet more realistically the exhibit hall was already large and full of cool stuff. But give me a break: Lyuba. This trumps everything. Going to see a real friggin’ frozen mammoth baby buries the needle of the awesomeness meter on the far right. That’s pretty much all I need to say. The spectacle was a spectacle.

This exhibit shows a lot of work, a lot of thought, and a personalized NHM touch that reflects the actual research (even very recent work!) that NHM staff like Prof. Lister are doing with collaborators around the globe. What more could we want, a herd of cloned mammoth babies frolicking around and tickling guests with their flanged trunks? Don’t hold your breath.

You’ve got just over 2 months to see the exhibit. Don’t come complaining on September 8 “BBBBBbbbut I didn’t know, I didn’t think it would be that cool! I just thought there’d be a guy in a Snuffleupagus suit signing autographs!” You have a duty as a Freezerino to go bask in the frozen glory of these Ice Age critters. There may be an exam at the end. 🙂

Is the exhibit kid-friendly? More or less. The text is more targeted at teenager-level or so, but the visual impact is powerful without it. I’d warn a sensitive child about the withered baby mammoth body before showing it to them, so they aren’t caught off guard and scarred by the experience. I saw plenty of kids in the exhibit and they all seemed happy. Parents may want to linger longer and absorb all the interesting information, whereas kids may blitz through or goof around, so plan accordingly if you’re inbound with sprogs.

You know what I was eyeing up in the gift shop...

You know what I was eyeing up in the gift shop…

Aside: The frozen mammoths get me wondering- what else does the Siberian (or extreme northern Canadian/Scandinavian) permafrost conceal? There are a lot of awesome Ice Age megafauna I’d cut my left XXXXX off to study quasi-intact… think about how amazing it would be to find a giant ground sloth (not bloody likely), sabretooth cat, or other species. There’s a lot of north up north. A lot of space and ice. A lot could happen. And climate change will make discoveries like this more likely, while the melting (and humanity) lasts…

Wool we ever find the Lyuba of woolly rhinos? It could happen.

Wool we ever find the Lyuba of woolly rhinos (Coelodonta)? Cast of a mummified woolly rhino from the NHM’s entry hall. More of these finds are likely, I’d say.

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